A wireless local area network (WLAN) technology has become one of major network access technologies because of its advantages of a high rate and low costs.
In a WLAN system, before transmitting data on a channel, a node needs to perform channel assessment on the channel based on a clear channel assessment (CCA) threshold. The node can transmit data on the channel if a result of the channel assessment is that the channel is idle. In a dense deployment scenario, coverage areas of a plurality of basic service sets (BSS) may overlap to form an overlapping basic service set (OBSS). A node in the OBSS can receive, on one channel, both a signal sent by another node in a BSS to which the node belongs and a signal sent by another node in the OBSS. In other words, a node in the OBSS can receive signals sent by nodes in different BSSs. If the node uses a same CCA threshold to perform channel assessment on signals that are sent by nodes in different BSSs and received on a channel, the channel assessment may be inaccurate. As a result, data transmission efficiency and a network throughput in the WLAN system are relatively low.
Therefore, it is extremely important to differentiate signals that are sent by nodes in different BSSs and received by a node.